1. Field of the Invention
The present invention relates to a positive type photosensitive paste composition for a plasma display panel (PDP) electrode, and more particularly, to a positive type photosensitive paste composition which hardly causes edge-curl and can obtain a high resolution micropattern.
2. Description of the Related Art
Generally, a plasma display panel (PDP) electrode is formed using a photosensitive paste having a conductive component by photolithography. FIG. 1 illustrates a process of forming an electrode using a conventional photosensitive paste through photolithography. In the process, a photosensitive paste 2 is applied to a surface of a substrate 1 and printed, and then dried to form a dried film 3. The dried film 3 is exposed using a UV exposing apparatus equipped with a photomask 4. Then, an uncured portion which is blocked by the photomask 4 is developed and removed with a developing solution. The remained cured film 5 is heat-treated to obtain a predetermined temperature to form a patterned electrode 6.
FIG. 2 illustrates a cross-section of a pattern after developing a conventional negative type photosensitive paste. Referring to FIG. 2, the patterned cured film has a cross-section of an inverted trapezoidal shape (so-called “under-cut”), in which a bottom portion is over-developed, after the developing process. An exposed region (a) and an unexposed region (b) are illustrated in FIG. 2. Since the dried paste film is almost composed of a conductive material which reflects and scatters light, a difference in the amount of light reaching the upper portion and the lower portion of the dried film is generated during exposing the (a) portion, thereby producing the under-cut. Thus, the under-cut is generated at exposed regions although the size of the under-cut is varied according to the type of paste. The formed under-cut acts as a primary factor in the occurrence of edge-curl (an edge portion of an electrode is curled) after heat-treating, the generation of residues (a portion around the heat-treated film is not clear), poor rectilinear path of a pattern, and poor resistance to sanding. These problems adversely affect important characteristics of the electrode, i.e., a withstand voltage, a resistance, resistance to sanding, etc. Thus, various methods for minimizing the under-cut have been proposed, but there is no method of preventing the occurrence of the under-cut.